In the prior art, and in particular from EP 2 047 879, a liquid-injection syringe is known of the type comprising a barrel of generally tubular shape forming a reservoir for the liquid and having fitted thereon an endpiece of generally annular shape for fastening a needle carrier on the syringe barrel.
The fastener endpiece is sometimes referred to as a “luer lock” and the needle carrier is sometimes referred to as a “luer hub”.
The syringe also has a plunger mounted to move axially in the barrel between a ready position and a position at the end of injecting liquid.
Below, an element is referred to as being “proximal” or “distal” depending on whether it is axially close to or far from the end of the plunger that is to be actuated by a user.
EP 2 047 879 also describes a safety device for such a syringe, the safety device comprising:
a first member of generally tubular shape, referred to as a “protective sheath”; and
a second member of generally tubular shape, referred to as a “syringe support”, that is received in the sheath, substantially coaxially therewith.
The protective sheath and the syringe support are movable axially relative to each other between two positions that are referred to below as the “disengagement position” and as the “retraction position” of the syringe needle. The syringe barrel is secured axially to the syringe support. For this purpose, a flange situated at the proximal end of the syringe barrel is prevented from moving axially in a housing situated between a bearing seat and retractable abutments of the support, the flange having a small amount of slack due to the dispersion in the dimensions of the syringe barrel.
The safety device enables the needle to be retracted automatically into the sheath so as to avoid a person being accidentally pricked with the needle when handling the syringe assembly after it has been used normally, i.e. after injecting the liquid into the body of a patient.
The fastener endpiece has a proximal end that is generally engaged on a distal end of the syringe barrel that is generally conical in shape.
Furthermore, the fastener endpiece has a distal end for co-operating by screw-fastening with a needle carrier. This needle carrier and the needle it carries are covered by a cap prior to utilization of the syringe. Where applicable, prior to putting the needle carrier into place on the syringe barrel, a plug for closing the syringe barrel is screwed onto the fastener endpiece.
The torque needed for unscrewing the plug or for screwing on the needle carrier can lead to the syringe barrel turning relative to the safety device. It is therefore appropriate to be able to prevent the fastener endpiece from turning, in particular so as to be able to unscrew the plug or to screw on the needle carrier.
Unfortunately, once the syringe has been mounted in the safety device, the fastener endpiece is generally made practically inaccessible by the protective sheath that covers it. The user therefore cannot act directly on the fastener endpiece in order to prevent it from turning, in particular while unscrewing the plug or while screwing on the needle carrier.
For that purpose, the device described in EP 2 047 879 has a syringe support provided with first means for securing it in turning about its axis and comprising at least one pawl urged resiliently into a position in which the pawl co-operates with complementary means carried by the fastener endpiece for securing them in turning.
That enables the endpiece and the syringe support to be prevented from turning relative to each other and thus facilitates the operations of unscrewing the plug and of screwing on the needle carrier.
Nevertheless, the means for securing the syringe support with the endpiece can be activated only when the endpiece placed on the syringe barrel presents a particular shape, and in particular a ribbed shape. It is therefore not possible to use such a device for preventing a syringe from turning if it does not present that specific endpiece.